Cylinder boss



Oct. 13, 1964 A. J. WEATHERHEAD, JR 3,152,718

CYLINDER Boss ,Filed March a, 1962 z sheets-snee@ 1 A T OEA/EVS oct 13; 1964 A. J. WEATHERHEAD, JR 3,152,718

CYLINDER BOSS 2 Sheets-Sheet 2 Filed March 8, 1962 INVENTOR. A L B51? .r WFA THEIEHEA, .7E-

United States Patent O 3,152,718, j Y ,y CYLINDER BSS Albert J. Weatherhearl, Jr., Shaker Heights, Ohio, assigner to The Weatherhead Company, Cleveland, Ohio, a corporation Vof Ghio j Filed Mar. S, 1962, Ser. No. 178,337

'2 Claims. (Cl. 2211-66) This invention relates generally to metal containers for compressed Vor liquied gases and more particularly to portable cylinders made from sheet metal for storing and ldispensing liquied petroleum gas.

Containers for transporting and storing compressed gases, particularly liquied petroleum gas, are generally formed as an elongated cylinder having substantially hemispherical caps on each end of the cylindrical cen-ter section. The top end cap is formed with a raised boss on its central portion which is provided with a threaded opening to receive the valve for controlling the flow of gas from the tank. In addition, this boss has a cylindrical outer wall portion which is threaded to receive a protective cap or guard which ts over the valve in order to prevent damage in transit. In addition to this, the boss generally has an annular portion which is stamped with the cylinder weight, and the manufacturers name and serial number, which are required by ICC regulations to identify the particular cylinder and its manufacturer.

Heretofore, pressure cylinders have generally been made in two different ways. In one of these methods, the threaded end opening is hot spun integrally with the cylindrical body which is fabricated by piercing and drawing from -a steel billet. With this method the cylinder boss portion can be made with extremely thick walls to give the necessary strength after the boss has been machined to provide the internal opening and interior and external threads. This method, which is generally usedron extremely high pressure, thick walled heavy cylinders requires relatively complex and expensive equipment and therefore has been replaced for liquied petroleum gas cylinders by methods of fabricating the cylinder body and end caps from sheet steel. However, it has not been previously possible with drawn steel end caps to provide suiciently thick material at the cylinder boss location to allow the cutting of the threads and the stamping of the necessary information on the boss while still maintaining the wall thickness required for strength and to comply with applicable regulations. Therefore, the end cap has generally been formed as a hemisphere having la centrally located opening about which is welded a cylinder boss assembly which is either machined from a heavier piece of metal or fabricated from a plurality of steel stampings. While this method has produced a cylinder boss having the necessary burst strength and other properties necessary to pass safety tests, it represents an undesirably complex manufacturing process to produce the separate cylinder boss structure and weld it in place on the formed end cap.

It is therefore a principal object of the present invention to provide an end cap for a relatively light weight pressurized gas cylinder in which the complete cylinder boss structure is integral with an end cap and formed from a single metal blank.

It is another object of this invention to provide a novel and improved method of making pressurized gas cylinders.

It is another object of this invention to provide a pressurized gas cylinder in which the end cap and cylinder boss are formed from a single blank of drawn steel in which the metal around a raised cylinder boss has a thickness at least as great as that of the remainder of the end wall and is provided with machined threads on its outer periphery and central aperture to receive the guard cap and valve, respectively.

3,152,718 Patented Oct. I3, 1964 rice It is another object of this invention to provide a one piece pressure gas cylinder end ca'p and cylinder boss which is at least as strong as end caps having welded cylinder boss inserts for the guard and valve receiving portions.

It is another object of this invention to provide a novel and improved seam for joining together adjacent portion of metal which provides maximum strength and freedom from leakage.

It is another object of this invention to provide a method of forming lapped joints between adjacent portion of sheet metal using a combination of resistance welding and copper brazing techniques.

It is still another object of this invention to provide a pressure cylinder for liquied petroleum 'gas which is simpler in construction and of lower cost in manufacture.

The foregoing and additional features and advantages of ythis invention will readily become apparent to those skilled in the art from the following detailed description of the preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a longitudinal cross-sectional view of a pressurized gas cylinder according to the present invention;

FIGURE 2 is a cross-sectional view through the cylindrical center section of the tank taken on line 2 2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary cross-sectional View of the cylinder boss;

FIGURE 4 is a fragmentary sectional view of the seam taken on line 4-4 of FIGURE 1; and

FIGURES 5 through l0 are cross-sectional views of the top end cap ofthe cylinder showing the successive drawing operations employed in forming the end cap and cylinder boss as an integr-al unit.

Referring now to the drawings in greater detail, and more particularly to FIGURE l, the pressure cylinder shown therein is formed completely from sheet steel and includes a cylindrical center section Ill, a top cap 11, and a bottom cap 12. The bottom cap 12 is lgenerally convex in shape and carries a foot ring 14 which is secured to the bottom cap 12 .along a continuous welded joint 15. The foot ring 14 serves as a support for the cylinder to hold it in an upright position, and is formed by bending from a strip of steel and welding the ends together along a butt joint 16. The lower edge of foot ring 14 has an inwardly and upwardly turned rimmed portion 18 to give the necessary s'treng'th at this point.

The cylindrical center section 1t) is formed by bending a sheet of steel into a cylindrical form and joining the edges together along a longitudinal seam indicated at 20. As shown in greater detail FIGURES 2, 4 and 5, the longitudinal seam 20 is of the lapped type in which one edge has a potioii 21 which is offset by the thickness of the steel sheet toward the inside' of the cylinder along the line 22. The other edge 24 therefore makes abutting contact along the offset line 22 and over-lapping contact along the offset portion 21. At the ends of the longitudinal seam 20, the offset portion 21 is cut away to form notched portions 25 so that the inner periphery of the cylindrical center section 10 is perfectly smooth at this point and the two edges make contact only along the oifset line 22. Top cap 11 and bottom cap 12 have cylindrical portions 27 and 28, respectively, which t within the cylindrical center section for a depth substantially equal to that of the notched portion 25. The caps 11 and 12 are thus joined to the cylindrical center `section 10 along continuous welds 31 and 32, respectively, and this weld is continued down toward along the offset edge 21 for a distance equal to the depth of the notched portion 25. Thus, the assembly of the center section 10 with the two end caps 11 and 12 produces a rigid and leak free cylinder.

A longitudinal seam is preferably formed by a cornbination of welding and brazing techniques. Although this seam could be formed with a continuous weld from end to end along the offset line 22, such a weld requires special holding fixtures because the localized heating of the metal would cause the formed cylindrical section to distort during welding and result in a non-cylindrical section which would prevent proper iitting of the end caps.

To overcome this problem, the longitudinal seam 20 is formed by bending the metal blank until the edge 24 overlaps the offset edge portion 21 and is in alignment with the offset line 22, after which the blank is held in this position by clamps at each end. The seam can then be secured in a strong, rigid, but not leak free manner by a number of spaced spot welds indicated at 34 in FIG- URE 1. The seam 20 is then finished and sealed by means of a brazing operation which provides a brazed joint for the full width of the longitudinal seam 20 and prevents any leakage at this point. This is done preferably by placing a thin strip or foil of copper or other suitable brazing material between the edge 24 and the offset portion 21 prior to the spot welding operation. This strip of brazing material is of the same width as the finished joint and preferably has a thickness between .002 and .006 inch. The spot welding at the points 34 is done after the foil is in place and the application of the spot welding current creates an arc through the foil which results in a localized melting and physical displacement of the copper in the area between the electrodes. Thus the thin copper or brazing metal foil is substantially removed from the spot weld area to permit a direct steel to steel weld of high strength as if the copper were not present. The spot welds rigidly secure the edges of the seam together without further clamping and the center section is then placed in a furnace at a temperature high enough to melt the brazing metal and allow it to adhere to the joint edges and secure them together in a strong and leak-free manner. Alternatively, the brazing can be accomplished after spot welding by placing a bead of brazing metal along the joint between the edge 24 and the olset line 22 so that when the center section is heated in a furnace, the brazing metal will ow into the space along the offset portion 21.

As shown in greater detail in FIGURE 3, the top cap 11 has a centrally located boss structure 36 which is formed integrally with the top cap. Top cap 11 is generally convex in shape so that the wall portion 37 is curved to extend substantially normal to the longitudinal axis of the tank at a point adjacent the boss structure 36. Boss structure 36 includes a cylindrical outer wall portion 39 which merges into wall portion 37 at its lower edge 40 and into a flat annular top wall portion 42 at the upper edge 43. At its inner edge 45, a top wall portion 42 merges into an inner cylindrical wall section 46 which extends inward into the tank where it terminates at a lower edge 47.

The outer cylindrical wall portion 39 is formed with threads 49 which receive a protective cap 50 of the usual kind adapted to extend over and cover the tank outlet valve. The inner cylindrical wall portion 46 is likewise provided with tapered pipe threads 52 to receive the outlet valve 53 from which a dip tube 55 extends downward toward the center portion of the tank.

Since the threaded portions 49 and 52 have the threads formed directly into the wall of the top cap, the wall at these points must be at least as thick as it is over the hemispherical portion 37 to give the tank the necessary burst strength. It is well known that when a flat blank is drawn into a cup the thickness of the sheet is thinned by the stretching that takes place over the face of the punch. This stretching and thinning of the wall is particularly pronounced in the drawing of hemispherical or conical cups, and the wall is thinned to the greatest extent at the center of the punch. Thus, if the top cap 11 were drawn directly to the final shape the wall of the boss structure 36 would be considerably thinner than the outermost wall portions and would therefore be too thin to allow forming of the threads 49 and 52.

For the above reason, applicant employs the drawing process shown in FIGURES 5 through 10 to avoid this thinning and stretching of the metal at the center of the blank. The blank is first cut to have an initial diameter approximately 25% greater than the finished diameter of the tank. This liat blank is then given a first draw to the sh ape indicated in FIGURE 5 having convex center section 53 and a radially extending ange 59. The second operation shown in FIGURE 6 draws the radially outer portion of the center section 58 of FIGURE 6 inward toward the plane of radial flange 59 to give a structure having a conical wall 61 sloping upward from flange 59, which remains unchanged, to a cylindrical wall portion 62 which terminates in a flattened top portion 63.

During the third, fourth and fifth operations shown in FIGURES 7, 8 and 9, respectively, the radial tiange 59 and the conical wall 61 remain unchanged, as does the diameter of the cylindrical Wall portion 62. In the third operation shown in FIGURE 7, the top portion is drawn inward in the center to form a shallow depression indicated at 65. At the same time, the top wall portion 63 is pressed downward to slightly thicken the cylindrical portion 62 and provide additional material for forming 'the depression 65 without substantially thinning the wall at that point. The fourth and fifth operations shown in FIGURES 8 and 9 show Athe depression 65 pressed progressively inward so that its depth is increased while its diameter decreases. The effect of this is to transfer some of the metal from the side walls 66 of depression 65 upward into the horizontal top portion 63. As a result of this transfer, the thickness is reduced only in the center portion 68 of the depression 65, and the thinning at this point is of no consequence because center portion 68 is subsequently punched out to provide the necessary opening to receive the valve.

The final operations are indicated in FIGURE l0 Where the radial flange 59 and conical wall 61 are drawn downward and inward to form the curved wall portion 71 and cylindrical portion 72 of the finished top cap. At the same time, the cylindrical portion 62 is reduced slightly in a sizing draw to the proper diameter before lthe threads are formed, and the centrally depressed portion 65 is struck from the underside to decrease the depth and thicken its side walls 66. After this has been done, the center portion 68 of the depression 65 lis punched out and the top cap is ready for the threading operations.

The threads 49 on the outer cylindrical wall 39 are preferably rolled to avoid removal of any metal at this point, while the inner threaded portion S2 has the threads cut to form a tapered pipe thread to give a leak-free seal at the valve. Since the cutting of the threads 52 decreases the wall thickness, and since the inner cylindrical portion 46 has its lower edge 47 unsupported, the effect of fluid pressure within the cylinder is such as t0 cause a reduction in diameter of the inner cylindrical wall portion 46 and thereby press the threads more tightly into engagement with the valve. Thus, this construction provides a pressure assisted seal at this point and any slight thinning of the wall 46 is not detrimental to the burst strength of the cylinder.

After the top cap 11 has been completely formed as described above, it is pressed into the cylindrical center section 10 and is preferably formed to have a diameter such kas to make this a relatively tight press lit. Subsequently, the bottom cap 12 is pressed into the other end of the cylindrical center section 10 in a similar manner and the welding completed around fthe portions indicated at 31 and 32 to form a pressure tight cylinder.

While the preferred embodiment of the pressure cylinder and the preferred method of making it have been shown and described in considerable detail, it is understood that this invention is not limited to such forms and methods, and various modications and rearrangements as will appear to those skilled in the art may be made without departing from the scope of the invention as set fonth in the following claims.

What is claimed is:

1. An end structure for a pressurized gas cylinder comprising a convex end wall and an integral raised centrally positioned cylinder boss for receiving an outlet valve and a cover, said cylinder boss including a cylindrical outer Wall projecting axially outward from said end wall, said outer wall being threaded on its outer surface to receive said cover, a flattened annular top extending radially inward from the outer edge of said cylindrical outer wall, and a cylindrical inner Wall extending axially inward from the radially inner edge of said top wall and threaded to receive an outlet valve, said cylinder boss and said end wall being of substantially uniform wall thickness and being drawn from an integral piece of sheet metal, said cylinder boss walls having a thickness substantially greater than the depth of the threads on the threaded portion so that the inner surfaces of the said boss walls are smooth and the threads on the threaded portions do not substantially reduce the bursting strength of the cylinder.

2. An end structure for a pressurized gas cylinder comprising a convex end wall and an integral raised centrally positioned cylinder boss for receiving an outlet valve and a cover, said cylinder boss including a cylindrical outer wall projecting axially outward from said end Wall, said outer wall being threaded on its outer surface to receive said cover, a attened annular top wall extending radially inward from the outer edge of said cylindrical outer wall, and a cylindrical inner Wall extending axially inward from the radially inner edge of said top wall and threaded to receive an outlet valve, said cylindrical inner wall having an axial length less than the axial length of said cylindrical outer wall whereby the inner edge of said inner wall is axially outward of the junction of said outer Wall With said convex end wall, said cylinder boss and said end Wall being of substantially uniform wall thickness and being drawn from an integral piece of sheet metal, said cylinder boss walls having a thickness substantially greater than the depth of the threads on the threaded portions so that the inner surface of said boss walls are smooth and the threads on the threaded portions do not substantially reduce the bursting strength of the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,713,675 Parish May 21, 1929 1,748,036 Draper Feb. 18, 1930 2,163,619 Murch June 27, 1939 2,255,802 Murch Sept. 16, 1941 2,312,637 Fulenwider Mar. 2, 1943 2,312,749 Bullock Mar. 2, 1943 2,322,845 Goldsworthy June 29, 1943 2,387,990 Grosser Oct. 30, 1945 2,444,833 Lampert July 6, 1948 2,460,721 Thompson Feb. 1, 1949 2,613,462 Johnson Oct. 14, 1952 2,664,222 King Dec. 29, 1953 2,727,301 Magnus Dec. 20, 1955 2,989,019 Van Sciver June 20, 1961 FOREIGN PATENTS 237,822 Great Britain Aug. 6, 1925 468,464 Italy Jan. 22, 1952 

1. AN END STRUCTURE FOR A PRESSURIZED GAS CYLINDER COMPRISING A CONVEX END WALL AND AN INTEGRAL RAISED CENTRALLY POSITIONED CYLINDER BOSS FOR RECEIVING AN OUTLET VALVE AND A COVER, SAID CYLINDER BOSS INCLUDING A CYLINDRICAL OUTER WALL PROJECTING AXIALLY OUTWARD FROM SAID END WALL, SAID OUTER WALL BEING THREADED ON ITS OUTER SURFACE TO RECEIVE SAID COVER, A FLATTENED ANNULAR TOP EXTENDING RADIALLY INWARD FROM THE OUTER EDGE OF SAID CYLINDRICAL OUTER WALL, AND A CYLINDRICAL INNER WALL EXTENDING AXIALLY INWARD FROM THE RADIALLY INNER EDGE OF SAID TOP WALL AND THREADED TO RECEIVE AN OUTLET VALVE, SAID CYLINDER BOSS AND SAID END WALL BEING OF SUBSTANTIALLY UNIFORM WALL THICKNESS AND BEING DRAWN FROM AN INTEGRAL PIECE OF SHEET METAL, SAID CYLINDER BOSS WALLS HAVING A THICKNESS SUBSTANTIALLY GREATER THAN THE DEPTH OF THE THREADS ON THE THREADED PORTION SO THAT THE INNER SURFACES OF THE SAID BOSS WALLS ARE SMOOTH AND THE THREADS ON THE THREADED PORTIONS DO NOT SUBSTANTIALLY REDUCE THE BURSTING STRENGTH OF THE CYLINDER. 